DNA and protein microarrays have become widely used tools for performing high throughput analysis in biology, medicine, chemistry, etc. One of the most promising platforms in microarrays manufacturing and application is based on three-dimensional (3D) gel substrates used for the immobilization of different kinds of probes forming microarrays. The last significant achievements in this area belong to the development of co-polymerization technology of microarray fabrication, also known as gel or hydrogel drop microarrays. Such microarrays are based on the co-polymerization of oligonucleotide, or peptide probes, modified with one or more unsaturated functional groups admixed with a gel-forming mixture, which is subsequently applied as a spot on glass or plastic substrate and allowed to polymerize under UV exposure to form a gel-drop microarray. The advantages of this methodology are that the produced 3D microarrays have a higher capacity for analyte detection than conventional microarrays, which may lead to increased sensitivity, especially for hybridization assays. By increasing the sensitivity of the hybridization assay, experiments providing the desired result are run using lower quantities of analyzed sample in comparison to conventional 2D microarrays. Additionally, 3D microarrays often provide a large amount of spacing between the immobilized probes; and allow for the creation of a water volume, which surrounds immobilized molecules. Furthermore, the efficiency and kinetics of the hybridization depend on a number of factors, including the diffusion rate of target DNA fragments and the accessibility of oligonucleotide probes.
Currently, microarrays affixed with DNA and peptides are widely utilized for the creation of platforms for various applications regarding nucleic acid and protein detection and identification. Such methods employ co-polymerization where the oligonucleotide or peptide probes are combined with the gel forming mixture, applied as a spot on a glass or plastic substrate and are polymerized via ultraviolet (UV) exposure to form the biochip. Detection and identification of genetic materials on DNA and protein biochips is based upon their interaction with target molecules isolated from biological samples with probes immobilized on gel elements. One method to increase the efficiency of hybridization is to improve the properties of the gel network used for the manufacture of the biochip. The most popular gel-forming compositions currently used are acrylamide and methacrylamide as gel-forming monomers, and methylenebisacrylamide as a cross-linking reagent. However, both of these widely used gel-forming monomers suffer from relatively high volatility and demonstrated low stability often resulting in spontaneous polymerization of co-polymerization mixtures. High volatility of monomers can cause significant changes in concentrations of copolymerization compositions during printing procedure especially for prolonged manufacturing process of microarrays containing numerous numbers of gel drops. Therefore resulting microarrays after polymerization will contain gel drops with different sizes and compositions that can lead to incorrect interpretation of results following hybridization experiments. It has also been observed that co-polymerization mixtures using acrylamide or methacrylamide as gel-forming monomers spontaneously polymerize and need to be operated and stored with special care if repeatedly used.
Developing new and novel approaches for the preparation of co-polymerization mixtures remains a difficult yet important task for microarray technology, and alternative and potentially optimal gel-forming monomers and cross-linkers that might be applicable to the manufacture of microarrays have yet to be studied.